Physical and chemical techniques will be developed for the analysis of the structure of complex macromolecular assemblies or organelles. The major goal is information on the conformation of individual assembled components and proximity relationships between components. Techniques will include singlet energy transfer fluorescence, breakable photocrosslinkers, phototransfer reagents and dye photosensitized chemical modification. A variety of potential uses for immunoglobulins and fragments directed against fluorescent dyes will also be explored including electron microscopy and affinity chromatography. These techniques will be applied to several different systems including the conformation of free and ribosome bound tRNA's structure of several ribosomal proteins, free and in the intact ribosome, the topological arrangement of proteins in the ribosome, protein-membrane interactions, and protein-protein interactions in complex multiprotein assemblies. A major focus for future work is expected to be protein-protein and protein-nucleic acid interactions in chromatin.